The invention relates to a lampholder which can suitably be used for a low-pressure discharge lamp which operates at a high frequency and which comprises an elongated, tubular discharge vessel, the lamp being provided with a pair of electrodes for maintaining an electric discharge in the discharge vessel. The lampholder has contacts for connecting a high-frequency power supply, the contacts being electrically connected to a first and a second terminal for connecting the lamp, the second terminal being further removed from the contacts than the first terminal.
The invention further relates to a lighting unit comprising a lampholder.
A lamp for use in such a lampholder is known from GB 2066559. This Patent document provides a solution for counteracting interference caused by high-frequency magnetic fields. Another type of interference is caused by conduction via the mains. In this type of interference, hereinafter also referred to as conducted interference, high-frequency voltage variations of the discharge arc with respect to ground cause a high-frequency current to flow from the lamp vessel, via parasitic capacitances between the lamp and ground, via ground, via parasitic capacitances between ground and the mains, and via the power supply back to the lamp vessel. Particularly in low-pressure discharge lamps which operate at high frequencies and which have a relatively long discharge vessel, for example in excess of 50 cm, this type of interference plays an important role as the relatively large surface of the discharge vessel results in a large capacitance between the discharge vessel and ground. This type of interference does not only cause interference at the frequency at which the lamp operates but also at higher harmonics thereof since the voltage across the interference sources, in particular the discharge arc and electrodes, deviates substantially from the sine shape.